A. Field of the Invention
The present invention relates to gelatinous elastomers, methods for making gelatinous elastomers, methods for using gelatinous elastomers, products made from gelatinous elastomers, and products which include gelatinous elastomers as a component or ingredient. More particularly, the invention includes a gelatinous elastomer formed from a combination of a block copolymer of the general configuration A-B-A and a plasticizer. The preferred A-B-A copolymer of the invention is an ultra high molecular weight polystyrene-hydrogenated poly(isoprene+butadiene)-polystyrene and the preferred plasticizer is either mineral oil or a combination of mineral oil and resin. Various other components may be included in the preferred recipes according to the invention.
B. Description of Related Art
For the benefit of the reader's comprehension of work that had been performed before the invention and the background against which the invention was made, an in-depth discussion of related and background art is provided below.
1. Early Oil-Extended Triblock Copolymer Compositions
U.S. Pat. No. 3,485,787, issued in the name of Walter R. Haefele et al., which is hereby incorporated by reference, discloses oil-extended triblock copolymers of the general configuration A-B-A, wherein A is an alkenyl aromatic hydrocarbon polymer block and B is a conjugated diene hydrocarbon polymer block. The '787 patent explains that alkenyl aromatic hydrocarbons are useful as the A blocks and that the B portion can be any four to ten carbon conjugated diene (col. 4, lines 4-7).
However, only polystyrene-polyisoprene-polystyrene, poly(.alpha.-methylstyrene)-polyisoprene-poly(.alpha.-methylstyrene) and polystyrene-polybutadiene-polystyrene are listed in the '787 patent as species of triblock copolymers suitable for use in that material (col. 3, lines 12-15). Although broad average molecular weight ranges are disclosed for each component (A having an average molecular weight of about 4,000 to 115,000 and B having an average molecular weight of about 20,000 to 450,000), test data is only listed for triblock copolymers wherein the A blocks each have an average molecular weight of about 15,000 to about 42,000 and the B blocks each have an average molecular weight of about 23,000 to about 75,000 (col. 5, line 74 and col.7, Table 3). Further, the '787 patent describes the amount of extending oil as 5 to 100 parts by weight based on 100 parts by weight block copolymer (i.e., about 2.5 weight percent to about 50 weight percent oil based on the combined weight of the oil and copolymer)(col. 2, lines 52-53 and col. 5, lines 21-23). While the tensile strength of those materials is high (typically greater than 1,000 psi)(col. 7, Table 3), their percent elongation is low (the highest stated value being 930%) (Id.). Further, Applicant believes that the materials of the '787 patent have a very high durometers when compared with the gelatinous elastomers of the present invention.
U.S. Pat. No. 3,676,387, issued in the name of James A. Lindlof, which is hereby incorporated by reference, discloses an oil-based elastomer which is five to thirty weight percent triblock copolymer of the general configuration A-B-A and seventy to ninety-five percent non-aromatic paraffinic oil (col. 2, lines 9-25). The patent defines A as a glassy or resinous non-elastomeric thermoplastic polymer block with a glass transition temperature above room temperature, having an average molecular weight of between about 2,000 and 100,000 and which is relatively incompatible with the elastomeric polymer block B (col. 1, lines 47-53). B is defined as an elastomeric polymer block of a conjugated diene, the average molecular weight being about 15,000 and about 1,000,000 and having a glass transition temperature considerably below that of the A blocks (col. 1, lines 53-57). The '387 patent also states that A:B weight ratios of 10:90 to 50:50 are useful (col. 1, lines 59-61). The oil weight percentage of the oil-extended elastomers of that patent, based on the combined weight of oil and elastomer, is in the range of 70% to 95% (col. 2, lines 9-25). The preferred materials of that patent have a low elasticity modulus, in the range of 1 to 10 psi for 200% elongation of a one square inch specimen (col. 1, lines 40-44). Applicant also believes that the preferred materials of the '387 patent have low tensile strength.
Although the '387 patent states that an average molecular weight range of 15,000 to 250,000 for the B mid-block is preferred and that the A blocks constitute from 10% to 50% of the total polymer weight (10:90 to 50:50 A:B weight ratios), the oil-extended elastomers were near the lower end of the disclosed weight ranges. One of the patent's examples describes an oil-extended elastomer which utilizes a styrene-butadiene-styrene block copolymer having an average molecular weight of only about 100,000, of which the average molecular weight of the B mid-block is about 70,000 (col. 3, lines 46-49). Thus, the styrene:butadiene weight ratio of that particular triblock copolymer is about 30:70.
Similar elastomeric materials are described in U.S. Pat. No. 3,827,999 issued in the name of Ronald K. Crossland, which is hereby incorporated by reference. That patent discloses block copolymers extended in 70 to 98 weight percent oil (col. 2, lines 8-9). The use of monoalkenylarene end blocks which are block polymerized with a conjugated diene is preferred (col. 2, lines 23-28). The average molecular weight range of the monoalkenylarene blocks used in Crossland's material is 5,000 to 75,000 (col. 2, lines 66-69). The average molecular weight range of the conjugated diene blocks used in that material is 25,000 to 250,000 (col. 2, lines 69-72).
However, the preferred block copolymers of that patent have a much lower average molecular weight: the monoalkenylarene blocks preferably having a molecular weight in the range of 8,000 to 65,000 and the conjugated diene blocks preferably having a molecular weight in the range of 35,000 to 110,000 (col. 2, lines 66-72). Moreover, the examples given in the patent utilized triblock copolymers of the general configuration A-B-A, wherein A represents a monoalkenylarene polymer and B represents a polymer composed of conjugated diene molecules, and having total molecular weights of only 57,000 (col. 4, line 3) and 70,000 (col. 4, line 2), with A:B ratios of about 33:67 and 29:71, respectively. The '999 patent states that the materials specifically preferred are polystyrene-hydrogenated isoprene-polystyrene and polystyrene-hydrogenated butadiene-polystyrene (col. 2, lines 55-59). Applicant believes that preference is due to the improved strength of materials which included triblock copolymers with hydrogenated midblocks over similar materials with non-hydrogenated midblocks, which were the subject of the '387 patent.
While Crossland states that his materials exhibit "no more than slight indications of bleeding as compared with the heavy bleeding which occurs with the compositions containing the non-hydrogenated block polymer" (col. 4, lines 43-46) and higher strength than similar materials with triblock copolymers having non-hydrogenated midblocks, they nonetheless exhibit very low tensile strength and poor elongation. Of the materials examined in the patent, the highest tensile strength (at break) noted was merely 80 psi (see tables at col. 3, lines 68-75 and col. 4, lines 57-64). The highest percentage elongation (at break) noted in the patent was only 850 (Id.). A further problem with Crossland's materials is the decrease in percent elongation with an increased amount of oil (Id.).
A styrene-ethylene butylene-styrene (SEBS) block copolymer, which has the general configuration A-B-A, is described in U.S. Pat. No. 4,176,240, issued in the name of Raffaele A. Sabia, which is hereby incorporated by reference. Sabia sought to meet a need for a more solid, handleable gel material (col. 2, lines 35-40). Sabia's material includes 5 to 10 weight percent SEBS, 87 to 93 weight percent naphthenic oil and 0 to 6 weight percent polyethylene, wherein all weight percentages are based upon the total weight of the material (Table I). Those materials are stated as having advantages for waterproofing (col. 2, lines 8-9), handling (col. 2, lines 35-40) and low temperature flexibility (See col. 2, lines 19-22, which identifies a need for such a property).
Sabia specifies that the SEBS useful in his material has a styrene to rubber ratio (A:B) of about 0.4 (i.e., 40:60)(col. 2, lines 33-44). In fact, the materials used in the examples had styrene to rubber ratios of 0.39 and 0.41 (i.e., 39:61 and 41: 59, respectively)(Table I, Constituent A). The experimental results listed in that patent demonstrate that Sabia's materials possess low tensile strength and low percent elongation. None of the results show a tensile strength of even 5 psi (Table I). The greatest amount of elongation shown is 129% (Id.).
Sabia states that during experimentation, styrene-isoprene-styrene (SIS) was used as a substitute for SEBS (col. 5, lines 33-35). However, he noted that the high amount of tackiness of the SIS-containing material made it less handleable and therefore undesirable (Id.).
In U.S. Pat. No. 4,259,540, also issued in the name of Sabia and which is incorporated herein by reference, the list of useful components for making compositions similar to those of the '240 patent was broadened. For example, in addition to naphthenic oils, the '540 patent describes use of paraffinic oils and mixtures of naphthenic and paraffinic oils (col. 2, lines 29-31). Similarly, the styrene to rubber ratio (A:B) range of the SEBS was increased from about 0.4 to approximately 0.2 to 0.5 (i.e., 20:80 to 50:50) and is stated as preferably being about 0.4 (col. 2, lines 35-38). In addition, a fourth element, isopropyl phenyl-phenyl phosphate, was added to the material to inhibit oil synersis, which implies that oil synersis may have been a problem with the material of the Sabia '240 patent (Table 1, footnote).
Despite Sabia's increased ranges in the '540 patent, the examples of that patent show no increase in either tensile strength or elongation over those of the '240 patent (Table 1).
U.S. Pat. No. 4,351,913, issued in the name of Naren I. Patel, which is hereby incorporated by reference, discloses a cable-insulative material that possesses properties similar to those of the materials described in the Sabia '240 patent, along with improved dielectric, high temperature drip and density characteristics. The material of the '913 patent includes a triblock copolymer of the general configuration A-B-A, chosen from SEBS, 7IS and styrene-butadiene-styrene (SBS)(col. 4, lines 11-14), and paraffinic or naphthenic mineral oil (col. 4, line 15). In addition, glass or ceramic microspheres and/or an additive may be used to make that material (col. 4, lines 19-20).
The examples of the '913 patent disclose mixtures composed of I to 30 weight percent styrene block copolymer, 52 to 82 weight percent either naphthenic or paraffinic mineral oil, 1 to 31 weight percent inorganic (e.g., glass or ceramic) hollow microspheres and 1 to 13 weight percent additive, if desired-such as polyethylene or glycerol hydroxy sterate (Table 3, the various constituents are identified throughout the text and tables).
Patel's preferred copolymers have very specific styrene to rubber (A:B) ratios: he prefers use of an SEBS having an A:B ratio of 0.39 to 0.41 (col. 4, lines 30-31), SBS having an A:B ratio of approximately 0.39 (col. 4, lines 37-38) or SIS having an A:B ratio of approximately 0.16 (col. 4, lines 42-43). Although use of other block copolymers in that material are noted, Patel's preferred formulations all include SEBS.
The '913 patent does not discuss the strength and elongation properties of the materials disclosed therein (col. 16, lines 65-68, which references Table 3, constituents A and B are identified at col. 4, 34-36).
2. John Chen's Thermoplastic Elastomer Gelatinous Compositions
Having familiarized himself with various gels available in the art, the inventor considers the gel compositions of John Chen to be the best available in the prior art, although the Chen gels are seriously deficient in several important areas, and these deficiencies are addressed by the invention.
U.S. Pat. No. 4,369,284, issued in the name of John Y. Chen, which is hereby incorporated by reference, discloses an oil-extended elastomer composition that includes about 6 to about 25 weight percent SEBS and about 75 to about 94 weight percent oil (col. 2, lines 8-24). The SEBS component of Chen's material has a styrene to rubber (A:B) ratio within the range of between 31:69 and 40:60 (col. 2, lines 25-34). Chen's preferred A:B ratio is 33:67 (col. 2, lines 30-31). However, according to Shell Chemical Company, KRATON.RTM. G1651, which is used in Chen's examples, has an A:B ratio of 32:68.
Chen's material is prepared by blending together the components including other additives as desired at about 23.degree. C. to about 100.degree. C., forming a paste-like mixture, and further heating said mixture uniformly to about 150.degree. C. to 200.degree. C. until a homogeneous molten blend is obtained (col. 3, lines 25-31). A heated vessel with a stirrer is all that is required to carry out Chen's melt blending process (Id.), although Chen's process takes many hours and much labor to complete.
The '284 patent discloses a 20 weight percent SEBS, 80 weight percent 200 weight paraffinic oil material which has a low breaking (i.e., tensile) strength of only 4.times.10.sup.6 dyne/cm.sup.2 (58 psi) and a low percent elongation of only 1,700% (Table I, col. 4, line 56 to col. 5, line 13). Further problems with Chen's material include relatively high amounts of oil bleed and tack (despite Chen's claim that the material was "substantially without oil bleedout" (col. 3, line 18)), each of which are unacceptable in various applications.
U.S. Pat. No. 4,618,213, issued in the name of John Y. Chen, which is hereby incorporated by reference, describes a material similar to that disclosed in Chen's previous patent applications and in the '284 patent. The material and the process for making the material are substantially the same as the material and process disclosed in the '284 patent. In the '213 patent, Chen again changed the average molecular weight range for plasticizing oils useful in the material, this time by stating that plasticizing oils having molecular weights of less than about 200 and greater than about 700 would be useful in his material (See col. 3, lines 29-31). The '213 patent also included a number of additional examples that did not appear in the '284 patent, including examples which listed the rigidity ranges of various materials having SEBS of different A:B weight ratios.
For each of the materials tested, depending upon the amount of oil used, rigidity ranged from about 20 to about 700 gram Bloom (Examples XI-XIV, col. 8, lines 15-45). However, Chen did not disclose any of the other physical properties of those materials. Therefore, Applicant believes that the tensile strength and percent elongation of those materials do not exceed the corresponding properties of the Chen material which contains 20 weight percent 33:67 SEBS and 80 weight percent of 200 weight paraffinic mineral oil (Table I, col. 6, lines 18-38). Chen does not state this specifically, however.
U.S. Pat. No. 5,262,468, issued in the name of John Y. Chen, which is hereby incorporated by reference, provides about the same basic disclosure of Chen's material as the '284 and '213 patents. However, in apparent realization that the molecular weight of the triblock copolymers of his composition provided beneficial physical properties such as tensile strength and percent elongation, Chen downplayed the importance of the SEBS A:B ratio, and broadened the A:B ratio range useful in his materials to about 20:80 or less to about 40:60 or higher (col. 3, lines 27-30). He stated that triblock copolymers having A:B ratios below 31:69 may be used, but they are less preferred due to their decrease in the desirable properties of the final composition (col. 4, lines 5-9).
Chen then noted the importance that, in combination with the A:B ratio range, the triblock copolymers used in his invention have a Brookfield solution viscosity of at least about 1,800 centipoises (cps)(col. 4, 36-42)(KRATON.RTM. G-1651 has a solution viscosity, 20% solids in 80% toluene, at 25-30.degree. C. of about 2,000 cps). Solution viscosity is related to the molecular weight of the copolymers. In addition, he included a long list of potential additives and more examples. However, no mention was made of the utility of many of the potential additives. Chen then listed several apparatus that could be made with his material.
One very interesting point about the '468 patent is the elongation at break value that is missing from Table I. Each of Chen's issued patents include a Table I, and the Table I of each patent is almost identical. However, Table I of every Chen patent which issued subsequent to U.S. Pat. No. 4,618,213 omits the elongation at break value.
Despite the missing elongation value, the '468 patent did not disclose a material with physical characteristics superior to those of the materials of Chen's '284 and '213 patents. Similarly, U.S. Pat. No. 5,508,334, which is hereby incorporated by reference, and which also issued in the name of John Y. Chen, disclosed a material having very similar composition and physical properties to those of the '284, '213 and '468 patents. The material of the '334 patent did, however, include the addition of a "minor amount" of various polymers to the material (col. 4, line 66 to col. 5, line 12). In the '334 patent, Chen's preferred gel is a mixture of (i) 100 parts by weight of a high viscosity poly(styrene-ethylene-butylene-styrene) triblock copolymer, (ii) from about 300 to about 1600 parts by weight of a plasticizing oil; and (iii) a minor amount of one or more homopolymers or copolymers (col. 2, lines 24-36). Applicant found the specification of the '334 patent confusing because it failed to identify the purpose of adding the homopolymers or copolymers to the material. SEBS useful in the material of the '334 patent has a Brookfield viscosity of not less than about 1,800 cps, and preferably about 2,000 cps or higher. Typically, the Brookfield viscosity values can range from about 1,800 cps to about 16,000 cps. Less typically, the Brookfield viscosity values can range from about 1,800 cps to about 30,000 cps or higher (col. 2, lines 37-45). However, KRATON.RTM. G-1651, Chen's preferred SEBS copolymer, has a Brookfield viscosity, 20% solids in 80% toluene, of only about 2,000 cps ('334, Table I, footnote 4). The '334 patent states that the styrene end block to ethylene and butylene center block ratios should be in the range of 20:80 or less to 40:60 or higher (col. 3, lines 11-14).
In addition, several patents which disclose articles made out of Chen's elastomeric materials have issued in the name of John Y. Chen. U.S. Pat. No. 4,618,213, which is hereby incorporated by reference, primarily discloses Chen's gelatinous material, but also states that objects such as lenses, rods, prisms and hemispheres can be made from his gel.
In U.S. Pat. No. 5,153,254, issued in the name of John Y. Chen, which is hereby incorporated by reference, Chen claims a reusable lint remover made from his gelatinous material. The patent does not contain a detailed description of such a device or of how it would be made.
U.S. Pat. Nos. 5,239,273 and 5,475,890, which are each hereby incorporated by reference, also issued in the name of John Y. Chen, each disclose reusable swabs made from Chen's gelatinous material. However, the A:B ratio range of the SEBS triblock copolymer used in that material--20:80 to 40:60--('890, col. 4, lines 6-9) is much broader than the SEBS A:B ratio range of the materials disclosed in the following Chen patents: '284 and '213.
U.S. Pat. No. 5,334,646, issued in the name of John Y. Chen, which is hereby incorporated by reference, claims an article of manufacture made from essentially the same material as that disclosed in Chen's '468 patent. Chen's list of articles of manufacture includes such things as a vibration damper, a vibration isolator, a wrapper, a hand exerciser, a dental floss, a crutch cushion, a cervical pillow, a bed wedge pillow, a leg rest cushion, a neck cushion, a mattress, a bed pad, an elbow pad, a dermal pad, a wheelchair cushion, a helmet liner, a hot or cold compress pad, an exercise weight belt, a swab, a traction pad, an orthopedic shoe sole, or a splint, a sling, or a brace cushion for the hand, wrist, finger, forearm, knee, leg, clavicle, shoulder, foot, ankle, neck, back or rib (col. 6, line 37 to col. 7, line 41). In addition, the '646 patent mentions that the material may be cast onto open cell substrates (col. 7, lines 38-59).
U.S. Pat. No. 5,336,708, issued in the name of John Y. Chen, which is hereby incorporated by reference, discloses a layered composite which includes layers of Chen's previously described materials physically interlocked with layers of other materials. The composite may contain more than one layer of Chen's materials, each layer having the same or different rigidities (col. 3, lines 11-13). The remaining layers are selected from the group consisting of foam, plastic, fabric, metal, concrete, wood, glass, ceramics, synthetic resin, synthetic fibers or refractory materials (col. 3, lines 40-45).
In the above-identified patents, Chen discloses various gel compositions which relate to poly(styrene-ethylene-butylene-styrene) (such as Shell's KRATON.RTM. G 1651), a plasticizing oil, and appropriate additives. Applicant, whose employer is a licensee of Chen's patents, found in working with Chen's gel that it had insufficient tensile strength, excessive oil bleed, and higher cost per unit volume. As described below, Applicant has created a gel, method for making the gel, and method for making articles from the gel that eliminates many of the problems found with the Chen gel.
Some of Chen's patents heavily emphasize the ratio of end block (A) to mid block (B) weights. Generally these ratios fall in the range of 19:81 to 52:49 (See, e.g., the '334 patent). Applicant believes that Mr. Chen attributed the more desirable performance of his gel, in comparison with the prior art, to the end block to mid block ratios. As explained below, Applicant's invention achieves substantially better performance than Chen's gel. However, Applicant believes that the material of the present invention performs better due to the chemical and physical characteristics of the particular A-B-A elastomer rather than because of the end block to mid block ratios of the A-B-A block copolymer.
As explained above, Chen prepared his gel compositions by blending together the components and additives at about 23.degree. to about 100.degree. C., forming a paste like mixture and further heating the mixture to about 105.degree. C. to 200.degree. C. until a homogeneous molten blend is obtained. Thereafter a desired article can be molded (See '334, col. 5, lines 25-45 for a description of Chen's gel manufacturing process). When Applicant's employer licensed Chen's patents, Chen instructed Applicant's employer on Chen's preferred gel composition and how to make it. The process was a complicated, multi-step process that took Applicant a long time to complete. Applicant believed there to be disadvantages in such a process because it was highly consumptive of energy and labor, required great amounts of time, and caused degradation of some of the gel components, so Applicant developed the quicker, simpler and cheaper processes explained below.
3. Post-Chen Oil-Extended Triblock Copolymer Compositions
Another relevant piece of prior art is Technical Bulletin number SC:1102-89, entitled "KRATON Thermoplastic Rubbers in oil gels," published by the Shell Chemical Company ("Shell Publication") which is hereby incorporated by reference. In the Shell Publication, mixing of Shell Chemical's triblock copolymers, which are marketed under the trade name KRATON.RTM., with oil under heat and shear is disclosed, as well as either increasing the rubber content of the blend or increasing the proportion of rubber segment in the molecule to increase oil retention.
U.S. Pat. Nos. 4,432,607 and 4,492,428, both issued in the name of Alvin C. Levy, both of which are hereby incorporated by reference, disclose oil-extended triblock copolymers (i.e., gels). Those patents describe materials made from styrene block copolymers and a plasticizing agent. The '607 and '428 patents disclose materials which include styrene-ethylene butylene-styrene (SEBS)('607, col. 3, lines 40-41; '428, col. 3, lines 52-53). Specifically, according to the '607 and '428 patents, Levy used KRATON.RTM. G1560 and KRATON.RTM. G1652, both manufactured by Shell Chemical Company of Houston, Tex., as the rubber component of his material ('607, col. 5, line 51; '428, col. 6, line 12). Both patents also state that Shell Chemical's KRATON.RTM. G1651 could be used as the rubber ('607, col. 5, lines 63-66; '428, col. 6, lines 24-27). The copolymers useful in those materials have a styrene to rubber (A:B) ratio of 0.2 to 0.5, and preferably of about 0.4 ('607, col. 2, lines 50-52; '428, col. 2, lines 65-67).
The plasticizer used in the materials of the '607 and '428 patents includes either naphthenic or paraffinic mineral oils or mixtures thereof ('607, col. 2, lines 45-47; '428, col. 2, lines 58-60). Optionally, the plasticizer may contain wax ('607, col. 2, line 60; '428, col. 3, line 8). The '607 and '428 patents state that, in the case of a single-layer or outer-layer coating, microcrystalline wax is preferred as a plasticizer ('607, col. 2, lines 60-62; '428, col. 3, lines 8-10).
In addition, according to the '607 and '428 patents, Levy seems to prefer materials with adhesive characteristics (See '607, col. 7, lines 44-47; '428, col. 8, lines 6-9). For this reason, Levy used resins which associate with the styrene end-blocks of the block copolymer, such as coumarone-indene copolymer or vinyl toluene--.alpha. methyl styrene copolymer, to provide adhesive characteristics to his material ('607, col. 2, lines 55-59; '428, col. 3, lines 3-6).
Both of these patents teach away from the use of high molecular weight rubbers, citing difficulty in blending with other components as the primary problem ('607, col. 5, lines 63-66; '428, col. 6, lines 24-27). Thus, it seems that the materials disclosed therein may have low tensile strength and inadequate elongation. Further, the high-adhesive properties (i.e., tackiness) of the preferred materials of the '607 and '428 patents are not desirable in many gelatinous elastomer (gel) applications.
U.S. Pat. No. 4,497,538, issued in the name of Naren I. Patel, which is hereby incorporated by reference, discloses a composition which includes SEBS block copolymers, petrolatum and polyethylene. According to the examples in the patent, SEBS makes up from 0.5 to 15 percent of the material (Table 1, col. 2, line 60 to col. 3 line 65). SEBS having a styrene to rubber (A:B) ratio of 0.39 to 0.41 is useful for purposes of that patent (col. 2, lines 4-6). Specifically, Patel prefers Shell Chemical's KRATON.RTM. G1650 and G1652 (col. 2, lines 7-10).
According to the examples, the compound of the '538 patent includes 80 to 93.5% petrolatum (Table 1). Petrolatum containing no more than about 15% oil, as determined by ASTM D 721, is preferred (col. 2, lines 12-14). Polyethylene makes up from about 1 to 15% of the material (Table 1). Polyethylenes that are considered useful in that material have a molecular weight in the 1,000 to 10,000 range and a specific gravity of greater than 0.90 (col. 2, lines 28-30).
Patel does not disclose physical properties such as strength or elongation, leading Applicant to suspect that the materials of the '538 patent have both little strength and little elongation. A further problem with the materials of the '538 patent are their low melting temperatures, in the range of 72.degree. C. to 117.degree. C. (Table 1).
The material disclosed in U.S. Pat. No. 4,509,821, issued in the name of Richard J. Stenger, which is hereby incorporated by reference, has a lower viscosity and a higher drip temperature (i.e., the temperature at which a material flows on its own, determined by placing a 20 gram sample in a three inch diameter dish which is positioned vertically within a forced air oven for two hours--drip temperature is often higher than melting point) than many of the prior art materials (col. 2, lines 61-63).
That material includes a plasticizing oil, SEBS and a linear polyethylene wax. The plasticizing oil, which makes up from 85 to 91% of the compound (Figure), is either naphthenic oil, paraffinic oil or a mixture thereof (col. 1, lines 59-64). The SEBS, which makes up from 5 to 10% of the material (Figure), has a styrene to rubber (A:B) ratio of from approximately 0.2 to 0.5, preferably of about 0.4 (col. 1, lines 64-67). Polyethylene wax having an average molecular weight in the range of about 1,000 to 1,500 (col. 1, line 67 to col. 2, line 1) makes up the remaining 2 to 8% of the material (Figure).
Applicant believes the materials of the '821 patent to be weak and have a low percent elongation. Further, the drip temperatures of those materials are relatively low and undesirable (See col. 2, line 55).
U.S. Pat. No. 4,709,982, issued in the name of Robert W. Corne et al., which is hereby incorporated by reference, discloses a gelled oil filling compound which includes a block copolymer having a molecular weight in the 200,000 to 2,000,000 range (col. 2, lines 34-35) and a hydrocarbon oil having an aromatic content of 12% or less (col. 2, lines 25-29). Corne's preferred block copolymer is Shell Chemical's KRATON.RTM. G1651, an SEBS copolymer (col. 3, lines 29-31). That material includes from about 1 to 10% SEBS (col. 2, lines 36-37), depending upon the oil characteristics (col. 3, lines 36-40). However, use of the material of the '982 patent seems to be limited to "gelled oil filling compound[s]" (claim 1).
Nevertheless, due to Corne's preferred use of KRATON.RTM. G1651 in that material, an SEBS triblock copolymer, Applicant believes the Corne compound to have low tensile strength and low percent elongation, just as Chen's material does. Applicant also believes, based upon the preferred copolymer of the '982 patent, that those materials possess undesirably high oil bleed and tack.
U.S. Pat. No. 4,716,183, issued in the name of Jose P. Gamarra et al., which is hereby incorporated by reference, discloses oil-extended styrene-diene block copolymers which include a cross-linked multifunctional coupling agent. In particular, the patent's examples all discuss the use of Shell Chemical's KRATON.RTM. G1650, KRATON.RTM. G1651, or a mixture thereof. The copolymers make up from about 2 to about 30 weight percent of the material, based upon the total weight of the material (col. 2, lines 3-4). The preferred embodiment contains from about 12 to about 22 weight percent block copolymer (col. 3, lines 10-11), and includes a combination of a KRATON.RTM. G1650-like material and a KRATON.RTM. G1651-like material in the range of about 40:60 to 60:40, based on the total copolymer weight (col. 2, lines 43-62). Cross-linking was performed for improved shape retention at higher temperatures (col. 2, lines 23-32). Gamarra et al. claim that cross-linking did not diminish the other physical properties of the material, such as tensile strength and percent elongation. No testing data that would tend to reveal those types of properties was provided for cross-linked materials.
Nevertheless, the non-cross-linked materials disclosed in the '183 patent, the strength of which was not diminished by cross linking, exhibit fairly low tensile strength and low elongation (Table, col. 4, line 57 to col. 5, line 20). Of the published results, the material having the greatest tensile strength and elongation had a 20 weight percent KRATON.RTM. G1651 copolymer component. The tensile strength of that material was only 142 psi, the elongation was only 1810%.
U.S. Pat. No. 4,798,853, issued in the name of Dale L. Handlin, Jr., which is incorporated herein by reference, describes a gel filling composition for cables which includes two to fifteen weight percent SEBS and 85 to 98 weight percent naphthenic or paraffinic oil or solvent having an aromatic content of up to 25 weight percent of the oil/solvent weight, the weight percentages of SEBS and oil being based upon the total composition weight (col. 2, lines 51-61). Most of Handlin's examples utilize Shell Chemical's KRATON.RTM. G1652. Oils/solvents having an aromatic content of about 15% are also preferred (col. 2, lines 60-61).
Applicant believes the materials of the '853 patent to have poor (i.e., low) tensile strength and elongation. Further, many of the materials described in the '853 patent have low gellation and dissolution temperatures, which vary depending upon the SEBS and the oil/solvent. According to the patent's examples, the gellation and dissolution temperatures of materials containing KRATON.RTM. G1652 ranged from about 15.degree. C. to about 60.degree. C. In contrast, a material containing the higher molecular weight KRATON.RTM. G1651 gelled at a temperature greater than 100.degree. C.
Pressure sensitive adhesives are the subject of U.S. Pat. No. 4,833,193, issued in the name of Sieverding. The adhesive materials of that patent contain from about 2 to about 40 weight percent triblock copolymer, alone or in combination with a diblock copolymer (col. 12, lines 8-14), at least 20 weight percent of a low molecular weight resin (col. 12, lines 15-18) and up to about 80 weight percent mineral oil having a viscosity of about 200 to about 1,200 (col. 12, lines 19-21).
Sieverding's preferred triblock copolymers are SEBS copolymers having essentially the same characteristics as KRATON.RTM. G1651 (col. 12, lines 38-40). Sieverding's most preferred high molecular weight SEBS has a styrene to rubber (A:B) ratio of about 0.48 to about 0.52 (i.e., about 48:52 to about 52:48)(col. 12, lines 40-45).
The '193 patent does not disclose the tensile strength of the materials described therein. Despite the possible increase in tensile strength, Applicant believes that the tensile strength of the materials of the '193 patent are low since SEBS is used in those materials.
U.S. Pat. Nos. 4,942,270 and 5,149,736, both issued in the name of Jose P. Gamarra, both of which are incorporated herein by reference, disclose gel compositions for use in cable sealing apparatus which are "nonmeltable" (i.e., begin to degrade, decompose or break down in some manner before they reach a temperature at which the composition will melt and become pourable). The compositions of those patents each include an SEBS triblock copolymer and oil. One of Gamarra's preferred SEBSs has a high molecular weight, particularly in the 250,000 to 280,000 range ('270, col. 4, line 64 to col. 5, line 1; '736, col. 4, lines 39-41), and a styrene to rubber ratio (A:B) of 33:67 ('270, col. 4, lines 46-48; '736, col. 4, lines 13-20). The SEBS sold by Shell Chemical as KRATON.RTM. G1651 was used for the patent's examples. While SEBS amounts of between about 2 and 30 weight percent of the total composition are disclosed, the preferred range is stated as 5 to 25 weight percent ('270, col. 4, lines 13-16; '736, col. 3, lines 51-56).
Oils which are useful in the compositions have molecular weights in the range of about 400 to about 2,500, and preferably in the range of 450 to 1,500 ('270, col. 5, lines 24-29; '736, col. 4, lines 64 to col. 5, line 1). Oil makes up from 70 to 98 weight percent of the composition, preferably from 75 to 95 weight percent ('270, col. 4, line 16; '736, col. 3, lines 50-51, 56). Gamarra prefers that the SEBS and oil are melt blended under high shear ('270, col. 2, lines 53-59, 65-66; '736, col. 2, lines 50-52, 63-64).
Gamarra notes that ultimate elongation of the compositions are from about 200% to about 1,200%. However, the preferred elongation range is about 400 to 1,100% ('270, col. 4, lines 22-26; '736, col. 3, lines 63-66). Such low elongation capability makes these materials undesirable for use in many applications. Further, although the patents do not list values for tensile strength, in light of the relevant SEBS-related prior art, Applicant believes that the materials of the '270 and '736 patents have low tensile strength.
U.S. Pat. No. 5,331,036, issued in the name of Jung W. Kang et al., which is hereby incorporated by reference, describes elastomer compositions which include copolymer compositions of 1,3-conjugated dienes and aromatic vinyl compounds having a weight average molecular weight of greater than about 1,000,000 and oil. Copolymers suitable for use in that material include, among others, midblocks (B) of 1,3-butadiene, 2,3-dimethyl-1,3 butadiene and 1,3 hexadiene (col. 4, lines 1-20). Kang prefers using styrene-butadiene-styrene block copolymers (col. 4, lines 58-60). The oil makes up from about 23 to about 75 weight percent of the composition, preferably greater than about 44 weight percent (col. 2, lines 47-50).
Physical characteristics such as tensile strength, elongation and Young's tensile modulus, durometer and rigidity are not provided by the '036 patent. Nor, to Applicant's knowledge, are the materials disclosed therein commercially available, even since Applicant interview the assignee of the '036 patent regarding those materials. Nevertheless, because of the extremely high molecular weight of the copolymers used in those materials, which is believed to result in entanglement of the rubber midblock, Applicant believes them to have low tensile strength and elasticity and high tensile modulus, high durometer and high rigidity measurements.
A gelatinous elastomeric material is needed which has improved elongation and tensile strength over the prior art, with comparable softness (i.e., durometer). A material is needed which has reduced oil bleed over prior art materials or no oil bleed, and reduced tack. Additionally, an elastomeric material which deforms easily under load and has a high level of shape memory is needed, exemplified by a rebound rate of about one second or less when a one inch long piece of the material is stretched to two inches an released.